Langmuir



I. LANGMUIR.

WIRELESS SIGNALING SYSTEM.

APPLICATION FILED IAN.29, I920.

Reissued Nov. 21, 192 2. I 15,495.

lnVehborl Irving Lrqmgmuir', by His Attorney.

Reimued Nov, 21 1922!.

FFlCE.

IRVING LANGMUIB, OF SCHENECIADY, NEW YORK, ASSIGNOR TO GENERAL: ELEC-- TRIO COMPANY, A GORIOBATION OF NEW YORK.

WIRELESS EIGNALING QYSTEM.

Original No. 1,313,093, dated August 12, 1919, Serial No. 83,637, filed March 11, 1916-. Application for reissue filed January 29, 1920. Serial No. 354,928.

To all whom it may concern:

Be it known that I, IRvING LANGMUIR, a

citizen of the United States, residing at Schenectady, in the county or" Schenec- 6 tady, State of New York, have invented -cer.ta1n 'new and useful Improvements in Wireless Signaling Systems, of which the following is a-specification.

My present invention relates to Wireless 10 signaling systems, and more particularly to an improvement in the so-called heterodyne system of wireless transmission. In this system it has been customary heretofore to provide at the receiving station .a

U5 source of sustained oscillations having afrequency slightly different from that of the waves used for transmitting the signals which it is desired to receive. Oscillations from this local source have been caused to :0 interact with the waves received from the distant station and produce, in a suitable device, signals, either visual or audible. In case the signals are rendered audible they may take the form of beats having a he 5 quency dependent on the difference in frequency-between the received and locally.

produced oscillations,

Various forms-of. apparatus for producing audible signals have been suggested.

l In my Patent 1,280,768, issued October 8,

1918, I have described a system in which the received and locally generated oscillations have been caused to interact and produce beats in a telephone receiver through the medium of an electron discharge device. In-

this case at least two separate agencies are re 'uired to efi'ectthe desired result,-namely, a evice for producing high frequency oscillations and an electron discharge device. I have discovered, however, that if an electron discharge device is'u'sed. as a source of oscillations it may at the same time serve as the agency throughwhich thetwo sets of oscillations interact to produce signals.-

.The novel features which I believe to be characteristic of my invention I have pointed out with particularity in the claims appended hereto; The invention itself, however, both as to the details of its organization and itsmode of operation will be bestunderstood by reference to the following de' scription takenln connection w1th the accompanying drawing in which I have shown from. any convenient source, as battery;

6.. The two electrodes are connected by an oscillatory circuit, containing an external source-of current 7,;which may be a battery, as shown,- or" any other direct current source, an inductance 8 and an (heating device which in this case takes,

the fonnQ-of telephone receiv'erfllO. The circuit thus formed. for convenience ,of desoriptionl call the plate circuit. The'cathode is also connected externally with the grid 5 through an inductance 9. The oscile'torycircuit thus formed designate the together by placing the inductance 8 in in ductive relation with theinductance 9. [80'- With the. circuit arrangement shown, if the grid circuit. The two circ its are coupled inductances- 8 and 9 are wouncLin the same direction, when current in the plate circuit begins 'to build up-cur'rent tends to flow in the opposite direction in the grid circuit and. the grid becomes negatively electrified. Thisf cuts down the flow of current in the plate circuit and as the current decreases thegrid loses its negative potential are becomes posi tiv'e. This allows the current to increase again in the plate circuit. These changes by varying the constants of; the/two circuitsby means otthe adjustable condensers 11 and 12plaoed respectively in the. 'grid'and plate circuits; cillations of any-desired frequency maybe obtained in the" coil- 9 and the: frequency 9.0 maytake place with great rapidity, their- .frequency depending upon the. naturalperiods of the two circuits. -The'frequ ency of the currentclranges maybe readily varied 95;

By. this means-sustained; -osma easily be adjusted to a value slightly di erent from thetcl' the waves which it 1swill always be in thesame direction. though in some cases it me be solarge that there is a. reversal in the irection of current-flow. In any case, however, the total current may be considered beiiiig made up of two componentsone of which is so oscillatory current.

Since in most cases it will be desirable to employ frequencies beyond the range of audibility of a'telephone receiver, these 10- cally produced current changes will have no effect in the receiver 10. If, however, the coil 9 is connected inductively with coil 13 of the grounded aerial l4,'the received oscillations will be impressed upon the grid 5 of the electron discharge tube. These oscillations 0- will produce a rapid variation in the potential of the grid which in turn will produce corresponding variations in the current Howbe certain periods when the two sets of cs ing through the tube, Inasmuch as the he quency of the received oscillations differs from the frequency of the current changes set up locally in plstecircuit there will cillations are in phase with each other when they will act together and produce increased changes in the current flow through the plate circuit. when they are directly opposite in phase and the currentchanges in the plate circuit will be correspondingly reduced. As a result of this action the current flowing through the telephone receiver 10 instead of having a. constant amplitude will have a regularly varying amplitude. Beats will consequently be heard in the receiver, the frequency of these beats being dependent upon the group frequency of the current variations produced in the plate circuit and this group frequency in turn being equal to the difference in frequency of the two sources. With this arrangement the only signals which can be received are those which are transmitted. by means of waves which differ in frequency from the locally w'oduced. os-

cillations by an amount which is within the range of sudibility of an ordinary tGlGPlIOYlP receiver. The Waves, whichdiflcr. in frequency from the locally produced waves by agreater or lessumount than the audil')le frequencyof. the receiver will produce no effect.

It will of ourse he understood that the current flowing; in the plate circuit is inade There will also be periodsup of a large number of rapidly succeeding HIXidiIECtlOHEtl impulses of brief duration. On account of the high fre uency of these impulses the inductance of t is receiver will tend to choke them back. To prevent this the condenser 15 may be shunted across the terminals of the receiver. In some cases it will be founddesirable to employ a bat: tery 16 in the grid circuit in order that normally the grid may have a. certain definite potential with respect'to the cathode.

The amount of;this potential will depend upon the design of the tube and upon the desired characteristics of the tube. It may be found advantageous in some cases to make the battery so lar e that the potential of the grid will always other hand it may be found desirable in some cases to so connect the battery that a positive potential will be imposed upon the cut that many modifications may be made without departing from'the spirit ofmy invention. I do not wish to be limited to the particular forms of apparatus indicated as other forms may also be used for the same purpose.

What I claim as new and desire to secure by Letters Patent of the United States, is 2-:

1. The combination in a wireless receiving.

system of an'antenna, an electrondischarge device having resonant plate and .grid ellcuits, inductances in each of said circuits which are coupled to each other whereby local oscillations may be produced of adif ferent frequency from that of the oscillations to be received, and a coil iii-said antenna which is coupledto both of said inductances.

2. The combination in a wireless receiving system of an antenna, an'electron discharge device having resonant plate and grid cii vcults, a coupling between said circuits where by local oscillations may be produced of a different frequency from that of the oscilla tions to be received, and a coupling between ouch-of said circuits and the antenna.

3. The combination in a wireless receiving system of an antenna, an electron discharge device having plate and grid circuits,o'ne of said circuits being resonant. inductanccs in each of said-circuits which are coupled to each other whereby local oscillations may be.

produced of a di crcnt frequency than that of the oscillations to be received and a-coil negative. On the- 5,495 i v a i in said antenna which is coupled to both of tions may be produced of a different fre-' said induct-ances. r quenc from that of the oscillations to be re 4. The combination in a wireless receiving ceivecl and a coupling between each. of said 10 system of an antenna, an electron discharge circuits and the antenna. 5 device having plate and grid circuits, one In witness whereof, I have hereunto set ofsaid circuits being, resonant, a,- coupling my hand this 27th daof January, 1920. between said circuits whereby local'oscilla- I IRV NG LANGMUIR: 

